Isoxazole derivatives and process for producing the same

ABSTRACT

The present invention provides isoxazole derivatives represented by the following formula (I):  
                 
 
(wherein R 1  represents a hydrogen atom, C 1 -C 20  hydrocarbon group or —C(═O)OR 1a  (wherein R 1a  represents a C 1 -C 10  alkyl group, etc.); R 2  and R 3  represent a hydrogen atom, halogen atom, hydroxy group, C 1 -C 20  alkyl group or C 6 -C 20  aryl group, etc.; R 4  represents a hydrogen atom, halogen atom, hydroxy group, cyano group, nitro group, amino group, C 1 -C 20  hydrocarbon group, C 1 -C 10  alkoxy group, C 1 -C 10  acyl group, 5- to 7-membered heterocyclic group, etc.; R 5  represents a hydrogen atom, halogen atom, hydroxy group, optionally substituted C 1 -C 20  hydrocarbon group, C 1 -C 20  alkoxy group, 5- to 7-membered heterocyclic group, etc.; and, n represents 0, 1, 2, 3 or 4), and a process of producing the same. The compounds are useful as intermediates for synthesis of pharmaceutical compounds, agricultural chemicals, dye compounds, etc. having the isoxazole skeleton.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent ApplicationSerial No. PCT/JPO2/13641, filed Dec. 26, 2002, which published inJapanese on Sep. 18, 2003 as WO 03/076419, claiming priority of JapanesePatent Application Serial No. 63588/2002, filed Mar. 8, 2002, and isincorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to isoxazole derivatives and a process ofproducing the same. More particularly, the present invention relates tointermediates useful for synthesis of pharmaceutical compounds,agricultural chemicals, dye compounds, etc. having the isoxazoleskeleton, and a process of producing the same.

BACKGROUND ART

Coleophomones A and B, which are represented by formulae (A) and (B)below, respectively, are naturally occurring substances having atransglycosylase activity and are compounds useful as antibacterialagents.

These coleophomones A and B are obtained by incubating Coleophoma sp.(MF6338). As shown by the formulae (A) and (B) described above, however,these compounds have a novel cyclic structure and thus, their chemicalsynthesis is unknown yet.

Accordingly, intermediates for synthesis of pharmaceutical compounds,agricultural chemicals, dye compounds, etc., including compounds havingsuch a complicated structure as well as a process of producing theintermediates have been desired.

DISCLOSURE OF THE INVENTION

The present invention provides isoxazole derivatives represented by thefollowing formula (I):

(wherein R¹ represents a hydrogen atom, optionally substituted C₁-C₂₀hydrocarbon group or —C(═O)OR^(1a) (wherein R^(1a) is an optionallysubstituted C₁-C₁₀ alkyl group, optionally substituted C₂-C₁₀ alkenylgroup or optionally substituted C₂-C₁₀ alkynyl group);

-   -   R² and R³, which may be the same or different, each        independently represents a hydrogen atom, halogen atom, hydroxy        group, optionally substituted C₁-C₂₀ alkyl group or optionally        substituted C₆-C₂₀ aryl group;    -   R⁴, which may be the same or different, each independently        represents a hydrogen atom, halogen atom, hydroxy group, cyano        group, nitro group, optionally substituted amino group,        optionally substituted C₁-C₂₀ hydrocarbon group, optionally        substituted C₁-C₁₀ alkoxy group, optionally substituted C₁-C₁₀        acyl group or optionally substituted 5- to 7-membered        heterocyclic group;    -   R⁵ represents a hydrogen atom, halogen atom, hydroxy group,        optionally substituted C₁-C₂₀ hydrocarbon group, optionally        substituted C₁-C₂₀ alkoxy group or optionally substituted 5- to        7-membered heterocyclic group; and,    -   n represents 0, 1, 2, 3 or 4).

In the general formula (I) described above, R¹ specifically represents ahydrogen atom, optionally substituted C₁-C₁₀ hydrocarbon group or—C(═O)OR^(1a) (wherein R^(1a) is an optionally substituted C₁-C₄ alkylgroup, optionally substituted C₂-C₄ alkenyl group or optionallysubstituted C₂-C₄ alkynyl group); more specifically a hydrogen atom orC₁-C₄ alkoxycarbonyl group; and most specifically a hydrogen atom,methoxycarbonyl group or ethoxycarbonyl group.

In the general formula (I) described above, R² specifically represents ahydrogen atom, optionally substituted C₁-C₄ alkyl group, optionallysubstituted C₂-C₄ alkenyl group or optionally substituted C₂-C₄ alkynylgroup; more specifically represents a hydrogen atom or C₁-C₄ alkylgroup; and most specifically a hydrogen atom or methyl group;

In the general formula (I) described above, R³ specifically represents ahydrogen atom, optionally substituted C₁-C₄ alkyl group, optionallysubstituted C₂-C₄ alkenyl group or optionally substituted C₂-C₄ alkynylgroup; more specifically represents a hydrogen atom or C₁-C₄ alkylgroup; and most specifically a hydrogen atom.

In the general formula (I) described above, specifically R⁴ may be thesame or different and each independently represents a hydrogen atom,halogen atom, hydroxy group, optionally substituted C₁-C₂₀ hydrocarbongroup or optionally substituted C₁-C₄ alkoxy group; more specifically,R⁴ may be the same or different and each independently represents ahydrogen atom, halogen atom, hydroxy group, C₁-C₄ alkyl group, C₁-C₄alkoxy group or C₁-C₄ alkoxy-C₁-C₄ alkoxy group; and most specifically,R⁴ may be the same or different and each independently represents ahydrogen atom, methoxy group or methoxymethoxy group.

In the general formula (I) described above, R⁵ specifically represents ahydrogen atom, halogen atom, hydroxy group, optionally substitutedC₁-C₂₀ hydrocarbon group, optionally substituted C₁-C₂₀ alkoxy group oroptionally substituted 5- to 6-membered heterocyclic group; morespecifically, R⁵ represents a hydrogen atom, halogen atom, hydroxygroup, C₁-C₄ alkoxy group or 6-membered heterocyclic group containing 1or 2 oxygen atoms; and most specifically, R⁵ represents a hydrogen atom,halogen atom, hydroxy group, methoxy group or 2,6-dioxycyclohexyl group.

In the general formula (I) described above, n is specifically 0, 1, 2 or3; more specifically 0, 1, or 2, further specifically 0 or 1; and mostspecifically 0.

Throughout the specification, the “C₁-C₂₀ hydrocarbon group” refers to ahydrocarbon group which may be saturated or unsaturated acyclic or mayalso be saturated or unsaturated cyclic and which may be either linearor branched when it is acyclic. Examples of the C₁-C₂₀ hydrocarbon groupinclude a C₁-C₂₀ alkyl group, C₂-C₂₀ alkenyl group, C₂-C₂₀ alkynylgroup, C₃-C₂₀ allyl group, C₄-C₂₀ alkyldienyl group, C₄-C₂₀ polyenylgroup, C₆-C₁₈ aryl group, C₆-C₂₀ alkylaryl group, C₆-C₂₀ arylalkylgroup, C₄-C₂₀ cycloalkyl group, C₄-C₂₀ cycloalkenyl group, (C₃-C₁₀cycloalkyl) C₁-C₁₀ alkyl group, etc.

More specifically, the C₁-C₂₀ hydrocarbon group used in the presentinvention includes a C₁-C₁₀ alkyl group, C₂-C₁₀ alkenyl group, C₂-C₁₀alkynyl group, C₃-C₁₀ group, C₄-C₁₀ alkyldienyl group, C₄-C₁₀ polyenylgroup, C₆-C₁₀ aryl group, C₆-C₁₂ alkylaryl group, C₆-C₁₂ arylalkylgroup, C₄-C₁₀ cycloalkyl group, C₄-C₁₀ cycloalkenyl group, etc.

In the specification, the “alkyl group” refers to an alkyl group whichmay be linear or branched, and examples include methyl group, ethylgroup, propyl group, n-butyl group, t-butyl group, pentyl group, hexylgroup, etc.

In the specification, the “alkenyl group” refers to a straight orbranched alkenyl group of 2 to 10 carbon atoms having 1 to 3 doublebonds. Specific examples include ethenyl, 1-propenyl, 2-propenyl,1-methylethenyl, 1-butenyl, 2-butenyl, 3-butenyl, 2-methyl-2-propenyl,1-pentenyl, 2-pentenyl, 4-pentenyl, 3-methyl-2-butenyl, 1-hexenyl,2-hexenyl, 1-heptenyl, 2-heptenyl, 1-octenyl, 2-octenyl, 1,3-octadienyl,2-nonenyl, 1,3-nonadienyl, 2-decenyl, etc.

The “alkynyl group” refers to a straight or branched alkynyl group of 2to 10 carbon atoms having 1 to 3 triple bonds and specific examplesinclude ethynyl, 1-propynyl, 2-propynyl, 1-butynyl, 2-butynyl,3-butynyl, 1-pentynyl, 2-pentynyl, 4-pentynyl, 1-octynyl,6-methyl-1-heptynyl, 2-decynyl, etc.

The “cycloalkyl group” refers to, for example, a cycloalkyl group having3 to 10 carbon atoms. Specific examples include cyclopropyl, cyclobutyl,cyclopentyl, cyclohexyl, cycloheptyl, etc. The lower cycloalkyl groupincludes a cycloalkyl group having 3 to 6 carbon atoms.

The “alkoxy group” refers to an oxy group, to which an alkyl group isbound and specifically includes methoxy, ethoxy, propoxy, 2-propoxy,butoxy, 1,1-dimethylethoxy, pentoxy, hexoxy, etc.

The “acyl group” includes, for example, formyl, acetyl, propanoyl,2-propanyol, pivaloyl, valeryl, pivaloyl, trifluoroacetyl, benzoyl,naphthoyl, nicotinoyl, methanesulfonyl, trifluoromethanesulfonyl,p-toluenesulfonyl, etc.

The “aryl group” includes, for example, phenyl group, a naphthyl groupsuch as 1-naphthyl group, 2-naphthyl group, etc., an indenyl group suchas 2-indenyl group, etc., an anthryl group such as 2-anthryl group,etc., a tolyl group such as 2-tolyl group, 3-tolyl group, 4-tolyl group,etc., biphenyl group, and the like.

The “heterocyclic group” includes a 5- to 7-membered saturatedheterocyclic group or unsaturated heterocyclic group having, forexample, 1 to 3 nitrogen atoms, oxygen atoms and/or sulfur atoms.Examples of the saturated heterocyclic group include tetrahydrofuryl,pyrrolidinyl, pyrazolidinyl, imidazolidinyl, piperidyl, morpholinyl,thiamorpholinyl and piperazinyl. Examples of the unsaturatedheterocyclic group include furyl, thienyl, indolyl, isothiazolyl, etc.

The groups which can be optionally substituted on the hydrocarbon group,the heterocyclic group, etc., include, for instance, a halogen atom(e.g., fluorine, chlorine, bromine, iodine, etc.), nitro group, cyanogroup, a C₁₋₆ alkyl group which may optionally be halogenated, a C₃₋₆cycloalkyl group which may optionally be halogenated, a C₁₋₆ alkoxygroup which may optionally be halogenated, a C₁₋₆ alkylthio group whichmay optionally be halogenated, hydroxy group, amino group, a mono-C₁₋₆alkylamino group (e.g., methylamino group, ethylamino group, propylaminogroup, isopropylamino group, butylamino group, etc.), a di-C₁₋₆alkylamino group (e.g., dimethylamino group, diethylamino group,dipropylamino group, dibutylamino group, ethylmethylamino group, etc.),formyl group, carboxy group, carbamoyl group, a C₁₋₆ alkylcarbonyl groupwhich may optionally be halogenated, a C₁₋₆ alkoxycarbonyl group (e.g.,methoxy carbonyl group, ethoxy carbonyl group, propoxy carbonyl group,tert-butoxycarbonyl group, etc.), a mono-C₁₋₆ alkylcarbamoyl group(e.g., methylcarbamoyl group, ethylcarbamoyl group, etc.), a di-C₁₋₆alkylcarbamoyl group (e.g., dimethylcarbamoyl group, diethylcarbamoylgroup, ethylmethylcarbamoyl group, etc.), a C₁₋₆ alkylsulfonyl groupwhich may optionally be halogenated, formylamino group, a C₁₋₆alkylcarboxamido group which may optionally be halogenated, a C₁₋₆alkoxycarboxamido group (e.g., methoxycarboxamido group,ethoxycarboxamido group, propoxycarboxamido group, butoxycarboxamidogroup, etc.), a C₁₋₆ alkylsulfonylamino group (e.g., methylsulfonylaminogroup, ethylsulfonylamino group, etc.), a C₁₋₆ alkylcarbonyloxy group(e.g., acetoxy group, propanoyloxy group, etc.), a C₁₋₆alkoxycarbonyloxy group (e.g., methoxycarbonyloxy group,ethoxycarbonyloxy group, propoxycarbonyloxy group, butoxycarbonyloxygroup, etc.), a mono-C₁₋₆ alkyl-carbamoyloxy group (e.g.,methylcarbamoyloxy group, methylcarbamoyloxy group, etc.), a di-C₁₋₆alkylcarbamoyloxy group (e.g., dimethylcarbamoyloxy group,diethylcarbamoyloxy group, etc.) and the like. The number of thesesubstituents to be substituted is not particularly restricted but thesesubstituents are substituted in 1 to 5, specifically in 1 to 3.

Next, the present invention provides a process of producing theisoxazole derivative represented by the following formula (I):

(R¹ represents a hydrogen atom, optionally substituted C₁-C₂₀hydrocarbon group or optionally substituted C₁-C₁₀ alkoxycarbonyl group;

-   -   R² and R³, which may be the same or different, each        independently represents a hydrogen atom, halogen atom, hydroxy        group, optionally substituted C₁-C₂₀ alkyl group, or optionally        substituted C₆-C₂₀ aryl group;    -   R⁴, which may be the same or different, each independently        represents a hydrogen atom, halogen atom, hydroxy group, cyano        group, nitro group, optionally substituted amino group,        optionally substituted C₁-C₂₀ hydrocarbon group, optionally        substituted C₁-C₁₀ alkoxy group, optionally substituted C₁-C₁₀        acyl group or optionally substituted 5- to 7-membered        heterocyclic group;    -   R⁵ represents a hydrogen atom, halogen atom, hydroxy group,        optionally substituted C₁-C₂₀ hydrocarbon group or optionally        substituted 5- to 7-membered heterocyclic group; and,    -   n represents 0, 1, 2, 3 or 4);        which comprises reacting the compounds represented by the        following formula (II):        (wherein R¹, R² and R³ are the same as stated above; Z        represents —O⁻M⁺ (wherein M represents Na, K or NEt₃), oxo or        hydroxy group; and the dotted line represents a chemical bond        when Z is —O⁻M⁺ or hydroxy group) with the compounds represented        by the following formula (III):        (wherein R⁴, R⁵ and n are the same as stated above; and Y        represents —C(X)═NOH        (wherein X is a halogen atom) or —CNO) in the absence of a        solvent or in a solvent inert to the reaction.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the process of the present invention is described in moredetail.

The isoxazole derivatives of the present invention can be produced,e.g., by the process shown by Scheme (I) below.

[wherein R¹, R², R³, R⁴, R⁵, Z, Y and n have the same significance asdescribed above].

In Scheme (I) described above, the compounds represented by generalformula (II) (especially the compound wherein Z is oxo) are reacted withthe compounds represented by general formula (III) in the absence of asolvent or in a solvent inert to the reaction; thus, the isoxazolecompounds represented by general formula (I) can be produced.

The solvents inert to the reaction which can be used for the reactiondescribed above, include, for instance, an alcohol type solvent such asmethanol, ethanol, isopropyl alcohol, etc.; an ethereal solvent such astetrahydrofuran, diethyl ether, etc.; a halogenated hydrocarbon typesolvent such as dichloromethane, chloroform, etc.; an aromatic solventsuch as benzene, toluene, etc.; a nitrile type solvent such asacetonitrile, etc.; an amide type solvent such as N,N-dimethylformamide,etc.; a ketone type solvent such as dimethyl ketone, etc.; a sulfoxidetype solvent such as dimethyl sulfoxide, etc.; water, and the like.These solvents may be used as an admixture of two kinds or more in anappropriate proportion. In the reaction above, a solvent mixture of analcohol such as ethanol and water (e.g., 2:1) is preferably used.

The reaction described above is carried out, for example, at atemperature of −78° C. to 150° C., preferably at 10° C. to 80° C. for0.1 to 144 hours, preferably 0.1 to 72 hours. This reaction is carriedout normally under ordinary pressure but, if necessary, can be carriedout under reduced pressure or under pressure.

On the other hand, the reaction of the compounds represented by generalformula (I) with the compounds represented by general formula (II) canalso be carried out in the presence of a catalytic amount of an aminebase. Examples of the amine base used herein include an aromatic aminesuch as pyridine, lutidine, etc.; a tertiary amine such astriethylamine, tripropylamine, tributylamine, cyclohexyldimethylamine,4-dimethylaminopyridine, N,N-dimethylaniline, N-methylpiperidine,N-methylpyrrolidine, N-methylmorpholine, etc. More specifically, thetertiary amine such as triethylamine, tripropylamine, tributylamine,cyclohexyldimethylamine, 4-dimethylaminopyridine, N,N-dimethylaniline,N-methylpiperidine, N-methylpyrrolidine, N-methylmorpholine, etc. arepreferably employed. The amount of the amine base used is 0.05 to 1.0mol, preferably 0.1 to 0.5 mol, based on 1 mol of the compound (II).

The reaction is carried out in the absence of a solvent or in a solventinert to the reaction. The solvents inert to the reaction which can beused in the reaction, include, for example, an alcohol type solvent suchas methanol, ethanol, etc.; an ethereal solvent such as tetrahydrofuran,1,4-dioxan, etc.; a halogenated hydrocarbon type solvent such asdichloromethane, chloroform, etc.; an aromatic solvent such as benzene,toluene, etc.; a nitrile type solvent such as acetonitrile, etc.; anamide type solvent such as N,N-dimethylformamide, etc.; a sulfoxide typesolvent such as dimethyl sulfoxide, etc.; 1,2-dimethoxyethane, water,and the like. These solvents may be used as an admixture of two kinds ormore in an appropriate proportion. Of these solvents, the alcohol typesolvent such as ethanol, etc. is preferably used.

The reaction described above is carried out, for example, at atemperature of −78° C. to 150° C., preferably at 0° C. to 100° C. andmore preferably at 20° C. to 80° C. for 0.1 to 50 hours, preferably 1 to50 hours and more preferably for 1 to 20 hours. This reaction is carriedout normally under ordinary pressure but, if necessary, can be carriedout under reduced pressure or under pressure.

In these reactions, a molecular sieve, a desiccant or the like canaccelerate the reaction. For example, 3 Å molecular sieve, 5 Å molecularsieve, basic alumina, etc. can accelerate these reactions. Therefore,these molecular sieves, desiccants, etc. are added to the reactionmixture in proper quantities.

The desired isoxazole compounds can be obtained from the reactionmixtures thus obtained, if necessary, by means of separation, e.g.,various chromatographies, etc.

When R¹ is —C(═O)OR^(1a), Z is —O⁻Na⁺ , and Y is —C(X)═NOH, the compoundof formula (I) can be synthesized by the process shown by Scheme (Ib)described below. The reaction conditions are the same as describedabove.

[wherein R¹, R², R³, R⁴ and n have the same significance as describedabove.]

According to a preferred embodiment of the present invention, theisoxazole derivatives represented by the following formula (I′):

can be obtained.

Next, the compounds represented by formula (II), which are used inSchemes (Ia) and (Ib) described above, are either publicly known or canbe synthesized by publicly known methods from publicly known compounds.The compounds represented by formula (IIa) can be synthesized by theprocess of Scheme (II) described below (e.g., see Edafiogho, I. O.,Hinko, C. N., Chang, H., Moore, J. A., Mulzac, D., Nicholson, J. M.,Scott, K. R., J. Med. Chem. 1992, 35, 2798-2805).

In Scheme (II) above, the compounds represented by general formula (II)can be obtained by reacting the 1,3-dicarbonyl compounds represented bygeneral formula (IV) with the ester compounds represented by generalformula (V) in the absence of a solvent or in a solvent inert to thereaction.

The solvents inert to the reaction which can be used for the reactiondescribed above, include, for instance, an alcohol type solvent such asmethanol, ethanol, etc.; an ethereal solvent such as tetrahydrofuran,diethyl ether, etc.; a halogenated hydrocarbon type solvent such asdichloromethane, chloroform, etc.; an aromatic solvent such as benzene,toluene, etc.; a nitrile type solvent such as acetonitrile, etc.; anamide type solvent such as N,N-dimethylformamide, etc.; a ketone typesolvent such as dimethyl ketone, etc.; a sulfoxide type solvent such asdimethyl sulfoxide, etc.; water, and the like. These solvents may beused as an admixture of two kinds or more in an appropriate proportion.In the reaction above, an alcohol type solvent such as ethanol, etc. ispreferably used.

The reaction described above is carried out usually in the presence of abase. Preferred examples of the base which can be used in this reactionare alkali or alkaline earth metal alkoxides such as sodium ethoxide,sodium butoxide, potassium ethoxide, potassium butoxide, etc.

The reaction described above is carried out at a temperature of, forexample, −78° C. to 150° C., preferably at 0° C. to 100° C. for 10minutes to 72 hours, preferably for 30 minutes to 12 hours. Preferably,this reaction can be carried out under reflux at a reflux temperature.This reaction is carried out normally under ordinary pressure but, ifnecessary, can be carried out under reduced pressure or under pressure.

Next, the compounds represented by formula (IIIa) used in Scheme (Ib)above (the compounds of formula (III) wherein R⁵ is OH and Y is—C(X)═NOH) are publicly known or can be synthesized from publicly knowncompounds by publicly known methods. For example, the compoundsrepresented by formula (IIIa) can be synthesized by the process ofScheme (III) described below (e.g., see Larsen, K. E., Torssell, K. B.G., Tetrahedron 1986, 40, 2985).

In Scheme (III) described above, the hydroximino compounds representedby general formula (III) can be obtained by halogenating the oximecompound of general formula (VI) with the halogenated imide compounds (Xis a halogen atom) represented by general formula (VII) in the absenceof a solvent or in a solvent inert to the reaction. In the halogenationany agent is usable so long as it is a safe halogenating agent. Otherchlorinating agents used herein include, for example, chlorine,hypochlorous acid, sulfinyl chloride, sulfonyl chloride, etc.

The solvents inert to the reaction which can be used for the reactiondescribed above, include, for example, an alcohol type solvent such asmethanol, ethanol, etc.; an ethereal solvent such as tetrahydrofuran,diethyl ether, etc.; a halogenated hydrocarbon type solvent such asdichloromethane, chloroform, etc.; an aromatic solvent such as benzene,toluene, etc.; a nitrile type solvent such as acetonitrile, etc.; anamide type solvent such as N,N-dimethylformamide, etc.; a ketone typesolvent such as dimethyl ketone, etc.; water, and the like. Thesesolvents may be used as an admixture of two kinds or more in anappropriate proportion. In the reaction above, the amide type solventsuch as N,N-dimethylformamide, etc. is preferably used.

The reaction described above is carried out, for example, at atemperature of −78° C. to 100° C., preferably at −78° C. to −60° C. for5 minutes to 72 hours, preferaby for 5 minutes to 36 hours.

The isoxazole compounds of the present invention thus obtained can beprovided for further reduction, esterification, alkylation, transferreaction, imine-forming reaction, cyclization, etc. to convert intouseful harmaceutical compounds, agricultural chemicals, dye compounds,etc.

EXAMPLES

Hereinafter the present invention is described with reference toEXAMPLES. However, the present invention is not deemed to be limited toEXAMPLES described below.

Example 1 Synthesis of ethyl3-(2-hydroxyphenyl)-6-methyl4-oxo4,5,6,7-tetrahydrobenzo[d]isoxazole-5-carboxylate

N,2-Dihydroxybenzenecarboximidoyl chloride in 100 mL of ethanol wasadded to sodium salt of ethyl 2-methyl4,6-dioxocyclohexanecarboxylate ina solvent mixture of 125 mL of water and 75 mL of ethanol at atemperature of 55° C. over an hour. The reaction mixture was maintainedat this temperature for 4 hours and then cooled down to roomtemperature. After diluting with water (100 mL), the mixture wasextracted with ethyl acetate (2×100 mL). The resulting extract waswashed with saturated sodium chloride aqueous solution (150 mL), driedover anhydrous sodium sulfate, and then concentrated under reducedpressure. The residue was treated with diethyl ether to give the product(2.48 g) as white powders. The residue was further purified by silicagel preparative thin layer chromatography to give additional 2.15 g ofthe product as white powders (total amount yielded at the 2 steps: 4.63g, yield: 60%). The physicochemical properties of the compound obtainedare shown below.

¹H NMR (400 MHz, CDCl₃)δ 9.38(br s), 8.57 (dd, 1H, J=7.9,0.7), 7.38 (t,1H, J=7.2), 7.07-7.00 (m, 2H), 4.28 (q, 2H, J=7.0), 3.38 -3.31 (m, 2H),2.95-2.89(m, 1H), 2.80 (dd, 1H, J=17.6,9.7), 1.32 (t, 3H, J=7.1), 1.25(d, 3H, J=6.5)

¹³C NMR (100.5 MHz, CDCl₃) δ 187.0, 180.4, 169.0, 159.7, 156.6, 132.7,131.8, 119.8, 117.3, 113.7, 112.2, 62.6, 61.6, 32.5, 29.7, 19.6, 14.2

IR (thin layer): 3230, 2974, 1739, 1691, 1590, 1428, 1445, 1253, 1023,751

Elemental Analysis (as C₁₇H₁₇NO₅) Calcd. C, 64.75%; H, 5.43%; N, 4.44%Found C, 64.53%; H, 5.45%; N, 4.25%

Example 2 Synthesis of(±)-3-(2-[1,3]dioxan-2-yl-6-methox&henvl)-6-methyl-6,7-dihydro-5H-benzo[d]isoxazol-4-one

(Step 1)

The compound (IIb) (4.8 mmols, 1.2 equiv) described above was added tothe compound (IIIb) (4.0 mmols, 1.0 equiv) described above in 30 mL ofisopropyl alcohol at room temperature. Thereafter, powdered 4 Åmolecular sieves (4 g, 1 g/mmol) were added to the mixture. Theresulting yellow slurry was heated to 50° C. and this temperature wasmaintained for 36 hours. The mixture was cooled to room temperature,then filtered, concentrated and purified by silica gel columnchromatography (1:1 hexane/EtOAc). The compound (Ib) described above wasobtained as white foam (3.24 mmols, yield: 81%).

(Step 2)

Triethylamine (NEt₃: 2.17 mmols, 1.40 equiv) was added to the compound(IIb) (2.32 mmols, 1.50 equiv) described above in 10 mL of ethanol atroom temperature. The solution obtained was warmed at 50° C. and stirredfor 24 hours at the temperature. After concentrating under reducedpressure, the concentrate was purified by silica gel columnchromatography (1:1 hexane/EtOAc) to give the compound (Ib) describedabove as white foam (1.36 mmol, yield: 88%).

The physicochemical properties of the compound (Ib) described above areshown below.

¹H NMR (400 MHz, CDCl₃)δ {1.21 (d, J=6.4 Hz), 1.23 (d, J=6.4 Hz), 3H},1.28-1.35 (m, 1H), 2.07-2.18 (m, 1H), 2.21-2.31 (m, 1H), 2.50-2.32 (m,2H), 2.68-2.77 (m, 1H), 3.15-3.24 (m, 1H), 3.61-3.69 (m, 1H), {3.71 (s),3.73 s, 3H}, 3.82-3.89 (m, 1H), 3.97-4.05 (m, 1H), 4.14-4.22 (m, 1H),5.46 (s, 1H), 6.97 (dd, 1H, J=7.4, 4.8 Hz), 7.38 (dd, 1H, J=7.4, 4.8Hz), 7.47 (t, 1H, J=7.4 Hz)

¹³C NMR (400 MHz, CDCl₃) δ 14.1, 15.5*, 20.5, 20.7*, 25.5, 25.7*, 30.2,30.7*, 30.9, 31.0*, 46.4, 46.6*, 55.8, 55.9*, 60.3, 61.2*, 67.0, 67.1*,67.1, 67.4*, 99.1, 99.4, 111.1, 111.2*, 112.2, 115.1, 116.0, 116.1*,118.2, 118.3*, 118.4, 127.2, 130.9, 130.9*, 138.7, 155.6, 155.7*, 157.6,157.8*, 179.7, 179.9*, 190.3, 190.5* (this compound is present in amixing ratio of 1:1 as an atropisomer; symbol * indicates the peaks,which became double intensity by the atropisomer.)

IR (thin layer) n 2964, 2884, 1694, 1599, 1479, 1446, 1272, 1075, 995.

Elemental Analysis (as C₁₉H₂₁NO₅) Calcd.: C, 66.46;H, 6.16;N,4.08;Found: C, 66.16;H, 6.27;N, 4.03.

Examples 3 through 14

The compound of formula (IIIc) described below was reacted with thecompound of formula (IIc) described below to give the compound (Ic) offormula described below. In EXAMPLES 3 and 4 and 10 through 14, thereaction was carried out in substantially the same manner as Step 2 ofEXAMPLE 2. In EXAMPLES 5 through 9, the reaction was carried out insubstantially the same manner as in EXAMPLE 1. The reaction conditions,yields, amounts yielded, etc. are shown in TABLE 1. TABLE 1

Amount of Base Amount Temp. the dione (quantity) Time Yield yielded EX.M Solvent (° C.) (Eq.) (Eq.) (min.) (%) (mmol) 3 NEt₃ CHCl₃ 60 5 NEt₃(5) 1080 <10 10.0 4 NEt₃ EtOH 0 1.0 NEt₃ (1.0) 60 60 1.5 5 Na EtOH roomtemp. 2.0 — — 62 1.0 6 Na toluene room temp. 2.0 — 15 83 1.0 7 Na(CF₃)₂CHOH room temp. 2.0 — 120 45 1.0 8 Na toluene room temp. 1.2 — 21082 1.0 9 Na CH₂Cl₂ room temp. 2.0 — 20 82 1.0 10 K toluene room temp.2.0 KHMDS (2.0) 120 35 1.0 11 Na toluene room temp. 2.0 NaHMDS (2.0) 6034 1.0 12 Na EtOH room temp. 2.0 NaOEt (2.0) 120 63 1.0 13 Na iPrOH roomtemp. 2.0 NaOiPr (1.8) 30 77 1.0 14 Na toluene room temp. 2.0 Na₂CO₃(2.0) 480 68 1.0In the table, Et and iPr represent ethyl and isopropyl, respecfively.

Examples 15 through 23

As shown in TABLE 2 below, the compound of formula (IIId) describedbelow was reacted with the compound of formula (IId) described below togive the compound (Id) of formula described below. In these EXAMPLES,the reaction was carried out in substantially the same manner as Step 2of EXAMPLE 2. TABLE 2

EXAMPLE Y R⁵ R^(4a) R^(4b) R² R¹ 15 —C(Cl)═NOH OH H H H H 16 —C(Cl)═NOHOH H H Me COOEt 17 —CNO * H OMe Me H 18 —CNO * H OmeOMe H H 19 —CNO *OMe H Me H 20 —CNO Br H OMeOMe H H 21 —C(Cl)═NOH OMe H H H H 22—C(Cl)═NOH Br H H H H 23 —C(Cl)═NOH H OMe H H H

In the table, *, Me and Et represent 2,6-dioxycyclohexanyl, methyl andethyl, respectively.

The reaction conditions, yields, amounts yielded, etc. are shown inTABLE 3. TABLE 3 Base Amount of (quan- Amount Temp. the dione tity) TimeYield yielded EX. Solvent (° C.) (Eq.) (Eq.) (min.) (%) (mmol) 15 iPrOHroom 2.0 NaOiPr 30 77 1.0 temp. (1.8) 16 toluene room 2.0 Na (-) 35 701.0. temp. 17 EtOH 50° C. 1.5 NEt₃ 1440 89 1.55 (1.5) 18 EtOH 50° C. 1.5NEt₃ 2160 76 0.6 (1.5) 19 iPrOH 50° C. 1.5 NaOiPr 1440 81 1.0 (1.4) 20iPrOH room 1.3 NEt₃ 1140 79 0.5 temp. (1.2) 21 iPrOH room 2.0 NaOiPr 3070 5.0 temp. (2.0) 22 iPrOH room 2.0 NaOiPr 5 62 1.0 temp. (2.0) 23iPrOH room 2.0 NaOiPr 35 64 1.0 temp. (2.0)

In the table, Et and iPr represent ethyl and isopropyl, respectively.

Industrial Applicability

According to the present invention, there can be provided intermediatesuseful for synthesis of pharmaceutical compounds, agriculturalchemicals, dye compounds, etc. having an isoxazole skeleton and aprocess of producing the same.

1. An isoxazole derivative represented by the following formula (I):

(wherein R¹ represents a hydrogen atom, optionally substituted C₁-C₂₀hydrocarbon group or —C(═O)OR^(1a) (wherein R^(1a) is an optionallysubstituted C₁-C₁₀ alkyl group, optionally substituted C₂-C₁₀ alkenylgroup or optionally substituted C₂-C₁₀ alkynyl group); R² and R³, whichmay be the same or different, each independently represents a hydrogenatom, halogen atom, hydroxy group, optionally substituted C₁-C₂₀ alkylgroup or optionally substituted C₆-C₂₀ aryl group; R⁴, which may be thesame or different, each independently represents a hydrogen atom,hydroxy group, cyano group, nitro group, optionally substituted aminogroup, optionally substituted C₁-C₂₀ hydrocarbon, optionally substitutedC₁-C₁₀ alkoxy group, optionally substituted C₁-C₁₀ acyl group oroptionally substituted 5- to 7-membered heterocyclic group; R⁵represents a halogen atom, hydroxy group, optionally substituted C₁-C₂₀hydrocarbon group, optionally substituted C₁-C₂₀ alkoxy group oroptionally substituted 5- to 7-membered heterocyclic group; and, nrepresents 0, 1, 2, 3 or 4):
 2. The isoxazole derivative according toclaim 1, wherein R¹ represents a hydrogen atom, optionally substitutedC₁-C₁₀ hydrocarbon group or —C(═O)OR^(1a) (wherein R^(1a) represents anoptionally substituted C₁-C₄ alkyl group, optionally substituted C₂-C₄alkenyl group or optionally substituted C₂-C₄ alkynyl group); R²represents a hydrogen atom, optionally substituted C₁-C₄ alkyl group,optionally substituted C₂-C₄ alkenyl group or optionally substitutedC₂-C₄ alkynyl group; R³ represents a hydrogen atom, optionallysubstituted C₁-C₄ alkyl group, optionally substituted C₂-C₄ alkenylgroup or optionally substituted C₂-C₄ alkynyl group; R⁴, which may bethe same or different, each independently represents a hydrogen atom,hydroxy group, optionally substituted C₁-C₂₀ hydrocarbon group oroptionally substituted C₁-C₄ alkoxy group; R⁵ represents a halogen atom,hydroxy group, optionally substituted C₁-C₂₀ hydrocarbon group,optionally substituted C₁-C₄ alkoxy group or optionally substituted 5-to 6-membered heterocyclic group; and, n represents 0, 1, 2 or
 3. 3. Theisoxazole derivative according to claim 1, wherein R¹represents ahydrogen atom or C₁-C₄ alkoxycarbonyl group; R² represents a hydrogenatom or C₁-C₄ alkyl group; R³ represents a hydrogen atom; R⁴, which maybe the same or different, each independently represents a hydrogen atom,hydroxy group, C₁-C₄ alkyl group, C₁-C₄ alkoxy group or C₁-C₄ alkoxy-C,-C₄ alkoxy group; R⁵ represents a halogen atom, hydroxy group, C₁-C₄alkoxy group or 6-membered heterocyclic group containing 1 to 2 oxygenatoms; and n is 0 or
 1. 4. The isoxazole derivative according to claim1, wherein R¹ represents a hydrogen atom, methoxycarbonyl group orethoxycarbonyl group; R² represents a hydrogen atom or methyl group; R³represents a hydrogen atom; R⁴, which may be the same or different, eachindependently represents a hydrogen atom, methoxy group ormethoxymethoxy group; R⁵ represents a halogen atom, hydroxy group,methoxy group or 2,6-dioxycyclohexyl group; and n is 0 or
 1. 5. Theisoxazole derivative according to claim 1, which is represented by thefollowing formula (I′).


6. A process of producing an isoxazole derivative represented by thefollowing formula (I):

(wherein R¹ represents a hydrogen atom, optionally substituted C₁-C₂₀hydrocarbon group or —C(═O)OR^(1a) (wherein R^(1a) is an optionallysubstituted C₁-C₁₀ alkyl group, optionally substituted C₂-C₁₀ alkenylgroup or optionally substituted C₂-C₁₀ alkynyl group); R² and R³, whichmay be the same or different, each independently represents a hydrogenatom, halogen atom, hydroxy group, optionally substituted C₁-C₂₀ alkylgroup or optionally substituted C₆-C₂₀ aryl group; R⁴, which may be thesame or different, each independently represents a hydrogen atom,halogen atom, hydroxy group, cyano group, nitro group, optionallysubstituted amino group, optionally substituted C₁-C₂₀ hydrocarbongroup, optionally substituted C₁-C₁₀ alkoxy group, optionallysubstituted C₁-C₁₀ acyl group or optionally substituted 5- to 7-memberedheterocyclic group; R⁵ represents a hydrogen atom, halogen atom, hydroxygroup, optionally substituted C₁-C₂₀ hydrocarbon group, optionallysubstituted C₁-C₂₀ alkoxy group or optionally substituted 5- to7-membered heterocyclic group; and, n represents 0, 1, 2, 3 or 4), whichcomprises reacting a compound represented by the following formula (II):

(wherein R¹, R² and R³ are the same as stated above; Z represents —O⁻M⁺(wherein M represents Na, K or NEt₃), oxo or hydroxy group; and thedotted line represents a chemical bond when Z is —O⁻M⁺ or hydroxy group)with a compound represented by the following formula (III):

(wherein R⁴, R⁵ and n are the same as stated above; and Y represents—CNO) in the absence of a solvent or in a solvent inert to the reaction.7. The process of producing the isoxazole derivative according to claim6, wherein the reaction is carried out in the presence of a catalyticamount of an amine base.
 8. The process of producing the isoxazolederivative according to claim 7, wherein the amine base is selected frompyridine, lutidine, triethylamine, tripropylamine, tributylamine,cyclohexyldimethylamine, 4-dimethylaminopyridine, N,N-dimethylaniline,N-methylpiperidine, N-methylpyrrolidine and N-methylmorpholine.
 9. Theprocess of producing the isoxazole derivative according to claim 7,wherein the amine base is used in 0.05 to 10 mol based on 1 mol of thecompound (II).
 10. The process of producing the isoxazole derivativeaccording to claim 6, wherein the reaction is carried out at atemperature of −78° C. to 150° C. for 0.1 to 144 hours.
 11. The processof producing the isoxazole derivative according to claim 10, wherein thereaction is carried out at a temperature of 10° C. to 80° C. for 0.1 to72 hours.
 12. The process of producing the isoxazole derivativeaccording to claim 6, wherein the solvent is selected from methanol,ethanol, tetrahydrofuran, diethyl ether, dichloromethane, chloroform,benzene, toluene, acetonitrile, N,N-dimethylformamide, dimethyl ketoneand water, and a mixture thereof.
 13. The process of producing theisoxazole derivative according to claim 6, wherein R¹ represents ahydrogen atom, optionally substituted C₁-C₁₀ hydrocarbon group or—C(═O)OR^(1a) (wherein R^(1a) represents an optionally substituted C₁-C₄alkyl group, optionally substituted C₂-C₄ alkenyl group or optionallysubstituted C₂-C₄ alkynyl group); R² represents a hydrogen atom,optionally substituted C₁-C₄ alkyl group, optionally substituted C₂-C₄alkenyl group or optionally substituted C₂-C₄ alkynyl group; R³represents a hydrogen atom, optionally substituted C₁-C₄ alkyl group,optionally substituted C₂-C₄ alkenyl group or optionally substitutedC₂-C₄ alkynyl group; R⁴, which may be the same or different, eachindependently represents a hydrogen atom, halogen atom, hydroxy group,optionally substituted C₁-C₂₀ hydrocarbon group or optionallysubstituted C₁-C₄ alkoxy group; R⁵ represents a hydrogen atom, halogenatom, hydroxy group, optionally substituted C₁-C₂₀ hydrocarbon group,optionally substituted C₁-C₄ alkoxy group or optionally substituted 5-or 6-membered heterocyclic group; n is 0, 1, 2 or 3; and, Z represents−O⁻M⁺ or oxo.
 14. The process of producing the isoxazole derivativeaccording to claim 6, wherein R¹ represents a hydrogen atom or C₁-C₄alkoxycarbonyl group; R² represents a hydrogen atom or C₁-C₄ alkylgroup; R³ represents a hydrogen atom; R⁴, which may be the same ordifferent, each independently represents a hydrogen atom, halogen atom,hydroxy group, C₁-C₄ alkyl group, C₁-C₄ alkoxy group or C₁-C₄alkoxy-C₁-C₄ alkoxy group; R⁵ represents a hydrogen atom, halogen atom,hydroxy group, C₁-C₄ alkoxy group or 6-membered heterocyclic groupcontaining 1-2 oxygen atoms; n represents 0 or 1; and Z represents−O⁻Na⁺ or oxo.
 15. The process of producing the isoxazole derivativeaccording to claim 6, wherein R¹ represents a hydrogen atom,methoxycarbonyl group or ethoxycarbonyl group; R² represents a hydrogenatom or methyl group; R³ represents a hydrogen atom; R⁴, which may bethe same or different, each independently represents a hydrogen atom,methoxy group or methoxymethoxy group; R⁵ represents a hydrogen atom,halogen atom, hydroxy group, methoxy group or 2,6-dioxycyclohexyl group;and n is 0 or
 1. 16. The process of producing the isoxazole derivativeaccording to claim 6, which comprises producing the isoxazole derivativerepresented by the following formula (I′).


17. The process of producing the isoxazole derivative according to claim6, wherein the reaction is carried out in the presence of a molecularsieve or alumina to accelerate the reaction.